This invention relates to road-imbedded traffic markers and their housings, including especially traffic markers embodying reflectors.
Traffic markers are installed in roads for the purpose of providing positive visual identification or delineation of the various traffic lanes at night, which is especially useful in wet or foggy conditions. Traffic lanes are usually defined by lines painted on the road surface, but in wet weather conditions the painted lines often become quite indiscernable, because of the deflection of the vehicles' headlight beams away from their source. To resolve this problem, reflectors are installed, with reflective surfaces protruding above the water film covering the road surface. When there are heavy snowfalls, the lines may become covered with snow. Road-imbedded traffic markers project slightly above the road surface and thus reduce or eliminate the problem, especially when embodying reflective elements.
Generally, road markers are positioned in line with the lines painted on the road surface, so that the lanes are thus clearly delineated. In addition, since the noise and vibration produced from driving over the markers deters drivers from doing so, there is then reduced wear on the painted markings, reducing the need for frequent repainting.
However, there are a number of problems associated with designing suitable traffic markers, especially in areas where snowfalls commonly occur. Any traffic marker must be able to stand up to repeated impacts from vehicle tires. In the case of traffic markers in snowfall areas, the markers must also be able to withstand the impact of snow removal equipment, especially snowplow blades, and at the same time must not unduly impede snow removal or produce excessive wear or damage to snowplow blades. The marker housing itself must be able to withstand impact, and the reflector should be protected to avoid separation from the housing, which has been a problem in the prior art.
Also, a traffic marker should preferably support its reflective surface or surfaces at approximately ninety degrees to the light source, i.e. approximately vertically. If the surface is angled, some light is inevitably reflected away from the source rather than back towards it, reducing the brilliance of the return signal and thus the effectiveness of the marker. There must also be some means by which the reflective surfaces are kept relatively clean, so that their reflective properties are preserved. In the case of a vertical reflective surface, this is particularly difficult to accomplish since road debris tends to pile up and accumulate against the surface. A reflective surface with an angled face is to some extent cleaned by the action of vehicles' wheels passing over it.
In some traffic markers in the prior art, cleaning of the reflective surfaces has been accomplished by providing for vertical movement of components when impacted, to wipe the reflective surfaces. Vertical movement has also been employed in the prior art to protect the markers by having them recede towards or beneath the road surface on impact, such markers being referred to as being "retractable".
Ideally the traffic markers should not be too complicated or expensive to manufacture, in view of the large quantities required. Retractable markers are obviously somewhat complicated in design. The markers should also be relatively simple to install in the road surface. Simplicity of installation is important not only from a cost viewpoint, but also in view of the need to minimize disruption to traffic during installation.